Polarity‐Controlled Attachment of Cytochrome C for High‐Performance Cytochrome C/Graphene van der Waals Heterojunction Photodetectors

Biomolecule/graphene van der Waals heterojunction provides a generic platform for designing high‐performance, flexible, and scalable optoelectronics. A key challenge is, in controllable attachment, the biomolecules to form a desired interfacial electronic structure for a high‐efficiency optoelectronic process of photoabsorption, exciton dissociation into photocarriers, carrier transfer, and transport. Here, it is shown that a polarity‐controlled attachment of the Cytochrome c (Cyt c) biomolecules can be achieved on the channel of graphene field effect transistors (GFET). High‐efficiency charge transfer across the formed Cyt c/graphene interface is demonstrated when Cyt c attaches with positively charged side to GFET as predicted by molecular dynamics simulation and confirmed experimentally. This Cyt c/GFET van der Waals heterojunction nanohybrid photodetector exhibits a spectral photoresponsivity resembling the absorption spectrum of the Cyt c, confirming the role of Cty c as the photosensitizer in the device. The high visible photoresponsivity up to 7.57 × 10⁴ A W^?1 can be attributed to the high photoconductive gain in exceeding 10⁵ facilitated by the high carrier mobility in graphene. This result therefore demonstrates a viable approach in synthesis of the biomolecule/graphene van der Waals heterojunction optoelectronics using polarity‐controlled biomolecule attachment, which can be expanded for on‐chip printing of high‐performance molecular optoelectronics.     

First‐principles study in an inter‐granular glassy film model of silicon nitride

Based on a previously constructed intergranular glassy film (IGF) model for bulk silicon nitride, a large periodic model of 3864 atoms containing 2 grains of different orientations from the main bulk β‐Si₃N₄ and 2 IGFs was fully relaxed using the ab initio density‐functional theory package VASP. The relaxed structure was then used to calculate the electronic structure, density of states, interatomic bonding, partial charge distribution, and electron localization using the OLCAO method. Analysis of the data focuses on the interfacial regions between bulk β‐Si₃N₄ and the Si‐O‐N glass layer with different orientations. The total bond order density (TBOD) is evaluated in different interfacial and bulk regions. We show minor differences in the internal cohesion between crystalline grains of different facets. However, the overall charges in the bulk crystal grains and in the glassy regions are electropositive which are balanced by the negatively charged interfacial region between the two. The presence of a less rigid glassy layer is the reason for structural flexibility in ceramics without a huge penalty in the steric energy. The optimization of the interfacial structure and bonding via the creation of defective sites is the atomic origin for the existence of the IGF in silicon nitride. The insights obtained from this detailed quantum mechanical analysis of a realistic IGF model are discussed including implications on the strength, fracture toughness, and processing methods. We also discuss the potential applications of our method to other complex materials systems.     

Tuberculosis in the newborn: an emerging disease

During the last three years 172 diagnostic laparoscopies (DL) were performed at our department in patients with an acute abdomen of unclear causes. This corresponds to 17% of all patients who underwent operation due to an acute abdomen in the same period. Always the indication for a diagnostic laparoscopy arose then, when the cause or the localization of the acute abdomen could not be found by conventional diagnostic methods. The advantages of DL were either the confirmation (93%) or the exclusion (7%) of the diagnosis "acute abdomen", the exact localization and simultaneously a definitive operative treatment of the cause by minimal invasive interventions (n = 109/65%). In these patients with acute abdomen the main causes were acute inflammations of gallbladder (n = 48) and appendix (n = 29), ulcus perforations (n = 9) and ileus (n = 9). The conversion rate amounted to 2.7%, the postoperative complication rate to 11% and the lethality rate to 1.8% in these patients. A new indication is the so-called "bedside laparoscopy" as means to control the postoperative course of mesenteric embolism (n = 9) and diffuse peritonitis (n = 3) in order to avoid the stress of a second-look operation for these seriously ill patients or to secure the indication for relaparotomy.     

A thermomechanical study on selective dispersion and different loading of graphene oxide in polypropylene/polycarbonate blends

Carbon nanofiller reinforced polymeric materials offer the opportunity to obtain materials with desired properties. In the present study, effects of different loading of graphene oxide (GO) on the compatibility, thermomechanical, and morphological properties of incompatible polypropylene (PP)/polycarbonate (PC) polymer blends were investigated. The neat blend and blend nanocomposites were prepared by using a twin‐screw extruder under controlled shear pressure to explore the role of GO on thermomechanical properties of blends. Fourier transform infrared analysis showed the presence of GO in PC phase which was further confirmed by differential scanning calorimetry and morphological analysis. It was observed that up to loading of 0.5%, GO preferable dispersed in only PC phase and then dispersed in both PP and PC phase with further increase in GO loading due to increase in viscosity of PC phase. Field emission scanning electron microscopy investigation of PNCs showed the coalescence of PC phase with increase of GO loading. Tensile analysis confirmed that 1% of GO loading produced highest reinforcement in thermomechanical properties and further increase of GO loading deteriorate the mechanical properties. Dynamic mechanical analysis also showed high storage modulus for 1% loading. Thermal stability of 1% GO loaded nanocomposite was found to be higher than other blend nanocomposites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45062.     

Influence of the extrusion process on the morphology and micromechanical behavior of polystyrene‐block‐(polystyrene‐co‐butadiene)‐block‐polystyrene star block copolymer/homopolystyrene blends

The influence of the extrusion process on the morphology and micromechanical behavior of an asymmetric polystyrene‐block‐(polystyrene‐co‐butadiene)‐block‐polystyrene (SBS) star block copolymer and its blends with general‐purpose homopolystyrene (hPS) was studied with films prepared with a single‐screw extruder. The techniques used were transmission electron microscopy and uniaxial tensile testing. Unlike the pure SBS block copolymer possessing a gyroid‐like morphology, whose deformation was found to be insensitive to the processing conditions, the mechanical properties of the blends strongly depended on the extrusion temperature as well as the apparent shear rate. The deformation micromechanism was primarily dictated by the blend morphology. The yielding and cavitation of the nanostructures were the principal deformation mechanism for the blends having a droplet‐like microphase‐separated morphology, whereas cavitation dominated for the blends containing macrophase‐separated layers of polystyrene. The mechanical properties of the blends were further examined with respect to the influence of the temperature and shear rate on the phase behavior of the blends. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Separation of phenol–water mixture by membrane pervaporation using polyimide membranes

Separation of components of aqueous waste streams containing organic pollutants is not only industrially very important but also is a challenging process. In this study, separation of a phenol–water mixture was carried out by using a membrane pervaporation technique with indigenously developed polyimide membranes. The membranes were found to permeate water selectively. The total flux as well as that of the individual components were measured. The effect of lithium chloride modification of polyimide film on total flux was investigated. The total flux obtained with 2% lithium chloride modification was about 3.6 times higher than that obtained with virgin membrane. The effects of different parameters such as feed composition and temperature on flux, and separation factor were determined. With modified membrane, a separation factor as high as 18.0 was obtained for water at 27°C and with 8.0 wt % phenol solution. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 822–829, 2002     

Blends of high density polyethylene and ethylene/1‐octene copolymers: Structure and properties

The morphology formation in the blends comprising a high density polyethylene (HDPE) and selected ethylene/1‐octene copolymers (EOCs) was studied with variation of blend compositions using atomic force microscopy (AFM). The binary HDPE/EOC blends studied showed well phase‐separated structures (macrophase separation) in consistence with individual melting and crystallization behavior of the blend components. For the blends comprising low 1‐octene content copolymers, the lamellar stacks of one of the phases were found to exist side by side with that of the another phase giving rise to leaflet vein‐like appearance. The formation of large HDPE lamellae particularly longer than in the pure state has been explained by considering the different melting points of the blend components. The study of strain induced structural changes in an HDPE/EOC blend revealed that at large strains, the extensive stretching of the soft EOC phase is accompanied by buckling of HDPE lamellar stack along the strain axis and subsequent microfibrils formation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1887–1893, 2007     

A linear hybrid methodology for improving accuracy of time series forecasting

Modeling and forecasting of time series data are integral parts of many scientific and engineering applications. Increasing precision of the performed forecasts is highly desirable but a difficult task, facing a number of mathematical as well as decision-making challenges. This paper presents a novel approach for linearly combining multiple models in order to improve time series forecasting accuracy. Our approach is based on the assumption that each future observation of a time series is a linear combination of the arithmetic mean and median of the forecasts from all participated models together with a random noise. The proposed ensemble is constructed with five different forecasting models and is tested on six real-world time series. Obtained results demonstrate that the forecasting accuracies are significantly improved through our combination mechanism. A nonparametric statistical analysis is also carried out to show the superior forecasting performances of the proposed ensemble scheme over the individual models as well as a number of other forecast combination techniques.     

Polyimide and nylon 6 blend film: Preparation,characterization and thermal behavior

A polyimide blend system has been prepared from a base polyimide of BTDAODA by adding ε‐caprolactam at the poly(amic acid) stage where ε‐caprolactam undergoes polymerization to form nylon 6 during the thermal cyclodehydration of poly(amic acid). The blend has been characterized by elemental analysis. IR, ¹³C CPMAS NMR, XRD and simple chemical methods. The thermal analysis study (TGA and DTA) shows that the stability of the blend systems is more in the lower temperature region (up to 300°C) in comparison to the control polyimide system. The isothermal study at 400°C in inert atmosphere shows that the blend system is equally stable but the isothermal study in air at 400°C shows that the thermooxidative stability of the blend films (except BB 4) is higher. Also, isothermal study in air at 500°C shows more than 90% weight loss for all the films within 3 h, but in an inert atmosphere, the blend films show lower weight loss compared to the control film. Although the XRD pattern of all the blend and control films shows an amorphous character, the films developed some crystallinity when treated with boiling NMP where the blend films developed higher crystallinity.     

Active noise cancellation in a suspended interferometer

We demonstrate feed-forward vibration isolation on a suspended Fabry-Perot interferometer using Wiener filtering and a variant of the common least mean square adaptive filter algorithm. We compare the experimental results with theoretical estimates of the cancellation efficiency. Using data from the recent Laser Interferometer Gravitational Wave Observatory (LIGO) Science Run, we also estimate the impact of this technique on full scale gravitational wave interferometers. In the future, we expect to use this technique also to remove acoustic, magnetic, and gravitational noise perturbations from the LIGO interferometers. This noise cancellation technique is simple enough to implement in standard laboratory environments and can be used to improve signal-to-noise ratio for a variety of high precision experiments.